Newton OS was the operating system for the Apple Newton PDAs produced by Apple from 1993-1997. Newton OS was written entirely in C++ and trimmed to be low power consuming and use the available memory efficiently. Similar to the original Apple Macintosh, many applications were written in the ROM of the Newton to save DRAM and flash space for user applications.

Newton OS featured many interface elements that even Mac OS didn't have at the time, such as drawers and the "poof" animation. An animation similar to this is found in Mac OS X, and parts of the Newton's handwriting recognition system have been implemented as Inkwell in Mac OS X.

Many features of the Newton are best appreciated in the context of the history of Pen computing, which is quite extensive.

Shortly after the Newton PDA's release in 1993, developers were not paying much attention to the new Newton OS API and were still more interested in developing for the Macintosh and Windows platforms. It was not until two years later that developers saw a potential market available to them in creating software for Newton OS. Several programs were made by third-party developers, including software to enhance Newton's initially disappointing (in OS 1.x) hand writing recognition technology.

Newton is a contraction of "New Town", the name of many places in English-speaking countries. It may refer to:

Sir Isaac Newton PRS MP (25 December 1642 – 20 March 1727 [NS: 4 January 1643 – 31 March 1727]) was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian, who has been "considered by many to be the greatest and most influential scientist who ever lived." His monograph Philosophiæ Naturalis Principia Mathematica, published in 1687, lays the foundations for most of classical mechanics. In this work, Newton described universal gravitation and the three laws of motion, which dominated the scientific view of the physical universe for the next three centuries. Newton showed that the motions of objects on Earth and of celestial bodies are governed by the same set of natural laws, by demonstrating the consistency between Kepler's laws of planetary motion and his theory of gravitation, thus removing the last doubts about heliocentrism and advancing the Scientific Revolution.